Our understanding of neurodegenerative diseases is currently hindered by lack of a firm neurobiological link between the patient's symptoms and the underlying neuropathology. To advance, we must identify not only key biochemical changes, but also how these changes alter the function of specific circuits to cause neurological symptoms. I seek to understand how impairment of particular circuits initiates early symptoms of Alzheimer[unreadable]s disease (AD), and how addition of further dysfunction leads to the disease's ultimate decline. I will apply a new method of selective neuronal silencing in transgenic mice to examine the behavioral impact of inactivating neuronal circuits damaged in AD. My postdoctoral laboratory has developed a novel chloride channel that responds specifically to ivermectin by producing hyperpolarization that results in selective, reversible suppression of neuronal activity. I will use my expertise in transgenic technology to create a mouse in which the ivermectin channel is conditionally expressed under control of Cre recombinase. Mating this mouse to animals expressing Cre in selected neuronal populations will allow those cells to be silenced with systemic ivermectin. My goal is to explore the function of adult-born hippocampal neurons, as this population is severely diminished in mouse models for AD. I will examine the role of these cells in learning and memory by selectively silencing them at critical times in the acquisition, consolidation, and recall of new information. Additional studies will address the effect of silencing on the migration, morphology, and survival of these adult-born cells. My long-term plans are to examine the behavioral impact of silencing other circuits damaged later in the course of disease to understand how diminished activity in multiple domains results in the progressive cognitive decline of AD. In the process, I will generate a transgenic mouse for selective neuronal silencing that will be broadly useful to the neuroscience community.